Analog data is most commonly organic information that is captured from the real world. For example, the light captured by film in a camera. Many of the things above have both analog and digital versions. For example, a clock with hands is analog as in theory the hand could constantly move at great precision. A clock with a numeric display is considered "digital" because its precision is exactly constrained to a unit such as minutes, seconds or milliseconds. In theory, a clock hand could have infinite variation between 12:01 and 12:02. A digital clock that displays hours, minutes and seconds would only have 60 variations between these two times. Analog is often described as having infinite precision. Generally speaking, this isn't strictly true. For example, a sound could be recorded at ever greater precision. However, the physics of the sound -- a propagation of energy through matter has some fixed representation that isn't infinite e.g. particles of air aren't infinitely small and their interactions aren't infinitely complex. Likewise, the precision of an analog device, recording, display, sensor or data recording isn't really infinite but is rather dictated by the physics of the events recorded and the devices recording them. For example, an LP record has physical limitations on the amount of information it can store and isn't a magical source of infinite information. It would be more accurate to say that a record has undefined precision as opposed to infinite precision. The human brain is analog. For example, we see streams of light as streams of electrical signals that create the perception of color.Digital technologies have the advantage that copies are exactly the same because they have known precision and well-defined attributes. When you copy analog signals, information is usually lost. It is commonly claimed that copying analog signals always results in information loss but this isn't strictly true as it is based on the questionable assumption that analog information is infinite. Analog computers are mostly experimental. However, it is very common for digital computers to interface with analog input and output devices. For example, a microphone that captures analog sound that gets converted to digital by a computer.Speakers and headphones create inherently analog sounds in the real world that is often converted from a digital source such as an mp3 file. Analog is often a continuous wave of information that is converted to digital with sampling. For example, the grey line (below) represents continuous sound that can be sampled as digital data at points as symbolized by the red arrows (below).
Analog Electronic Circuit
Clocks (with hands)
Dial (e.g. volume dial on a stereo)
Light & Color
Sensors (e.g. gyroscope)